Problem 1 Difficulties with postoperative fluid balance in a 58-year-old man
The provisional diagnosis is this patient probably has small bowel obstruction secondary to adhesions.
Blood is collected for haematological and biochemical analysis and an IV cannula placed for fluid replacement. Abdominal and chest radiographs are ordered. A urinary catheter is inserted and 350 mL concentrated urine drains. A NG tube is placed and 800 mL faeculent fluid is drained within the first 2 hours. His blood results are as follows:
Investigation 1.1 Blood results
Haemoglobin | 165 g/L |
White cell count | 9.6 × 109/L |
Platelets | 350 × 109/L |
Sodium | 149 mmol/L |
Potassium | 3.4 mmol/L |
Urea | 10.0 mmol/L |
Creatinine | 0.12 mmol/L |
Chloride | 112 mmol/L |
Bicarbonate | 29 mmol/L |
Glucose | 4.4 mmol/L |
Bilirubin | 19 µmol/L |
Total protein | 65 g/L |
Globulins | 27 g/L |
Albumin | 38 g/L |
ALT | 25 U/L |
AST | 39 U/L |
ALP | 74 U/L |
GGT | 17 U/L |
LDH | 110 U/L |
Amylase | 65 U/L |
Calcium | 2.16 mmol/L |
Phosphate | 1.15 mmol/L |
Uric acid | 0.21 mmol/L |
Cholesterol | 3.6 mmol/L |
His abdominal X-ray is shown in Figure 1.1.
Over the next 12 hours the patient’s symptoms fail to improve. His pain becomes more severe, initially more frequent and then constant. He develops increasing abdominal distension and tenderness. He becomes pyrexial.
Conservative management has not been successful and an emergency operation is arranged.
At operation there are multiple adhesions involving the small bowel. These are released. A small segment of small bowel is strangulated, necrotic, but not perforated. This is resected and a primary anastomosis formed. A drain is placed.
The morning after his operation the patient looks reasonably well and is afebrile. He continues on prophylactic intravenous antibiotics and is on patient-controlled narcotic analgesia. His blood pressure is 130/90 mmHg and his pulse rate is 90 bpm. His fluid balance chart for the 24 hours since admission is as follows:
Investigation 1.2 Fluid balance chart on admission
Fluid Input | |
IV fluids | 4200 mL |
Fluid Output | |
Urine total | 400 mL |
Urine last 4 hours | 22/16/12/0 mL |
Nasogastric tube | 700 mL |
Wound drain | 200 mL |
With a bolus of 500 mL isotonic saline the urine output is increased to 50 mL over the next hour. A maintenance regimen of 1 L of isotonic saline is ordered, to be followed by 1 L dextrose 5% at 100 mL/hour and a replacement regimen of isotonic saline at 50 mL/hour using an infusion pump.
On review the following morning the patient had been given an additional 500 mL of dextrose 5% overnight when his urine output fell over a 4-hour period to less than 20 mL/hour. He now feels thirsty and there is loss of skin turgor. His abdomen is mildly distended, with absent bowel sounds, but soft and non-tender. His blood pressure is 110/65 mmHg on lying and 90/60 mmHg on sitting. His pulse rate is 100 bpm and he has a dry tongue. His fluid balance chart for the previous 24 hours shows the following:
Investigation 1.3 Fluid balance 24 hours later
Fluid Input | |
IV fluids | 3700 mL |
Fluid Output | |
Urine total | 800 mL |
Urine last 4 hours | 15/13/9/8 mL |
Nasogastric tube | 2800 mL |
Wound drain | 400 mL |
The early morning electrolytes are as follows:
Investigation 1.4 Electrolytes
Sodium | 138 mmol/L |
Potassium | 2.7 mmol/L |
Chloride | 102 mmol/L |
Bicarbonate | 29 mmol/L |
Urea | 7.0 mmol/L |
Creatinine | 0.08 mmol/L |
Q.6
Comment on this man’s fluid balance and electrolytes. What fluids should be given to the patient over the next 24 hours?

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